Pierce the lamb fillet and fill with slivers of garlic. Brush with lemon juice and olive oil and set aside.
Heat the oil in a baking tray. Add the artichokes and Spanish onion and season with sea salt and black pepper. Bake for 20 - 25 minutes.
While the artichokes are cooking chargrill the lamb for approx 7 minutes each side. Leave to rest for 5 minutes before serving the lamb on the onion and artichoke. Top with a spoon of the rocket pesto.
Serve with a dressed green salad or steamed English spinach.
Note: Wrap Jerusalem artichokes in kitchen paper and store them in a plastic container in the fridge.